1. Field of the Invention
The present invention relates to a track work machine for excavating material from a bed supporting a track comprised of ties defining cribs therebetween and rails fastened to the ties, which comprises a machine frame extending in a longitudinal direction, undercarriages supporting the machine frame on the track for movement in an operating direction, a vertically adjustable endless excavating chain operable to be trained, and revolve, around the rails in a plane inclined relative to the longitudinal direction, and a ballast clearing device mounted on the machine frame between the undercarriages, the ballast clearing device comprising a vertically and transversely adjustable clearing tool.
2. Description of the Prior Art
A track work machine of this general type has been disclosed in U.S. Pat. No. 4,108,076. To enable this machine to operate on a track-free section of the ballast bed, the machine frame carries caterpillar undercarriages. A ballast clearing device arranged immediately ahead of the endless excavating chain is comprised of two transversely spaced, vertically and transversely adjustable endless scraping chains revolving in a horizontal plane. The scraping chains enable the operating width of the excavating chain to be increased. As explained in the patent on top of column 5, before the start of the operation, a ditch must be dug in the ballast bed under the track, either manually or by some auxiliary equipment, to permit the previously opened endless excavating chain to be passed transversely under the track. This is cumbersome and delays the operation of the machine.
U.S. Pat. No. 5,553,674 also discloses a track work machine for excavating ballast from a track bed, which comprises a ballast clearing device immediately preceding an endless excavating chain. The ballast clearing device is comprised of a vertically and transversely adjustable suction pipe connected by a flexible suction hose to a vacuum device. In this way, the required ditch for insertion of the excavating chain under the track can be produced. The suction pipe is immersed in the ballast and a sufficient amount of ballast is aspirated to create the ditch.